1. Field of the Invention
The present invention relates to a system and method for supplying fuel to an internal combustion engine of a vehicle which cuts off the supply of fuel when a predetermined engine operating condition is satisfied.
2. Description of the Prior Art
Conventionally, the system for supplying fuel to the internal combustion engine for a vehicle cuts off supply of fuel when the output power of the engine is not needed, such as during deceleration, in order to conserve fuel.
Conventional systems as described above are exemplified by U.S. Pat. No. 4,395,984 filed on Sept. 25, 1980. There is, however, a problem in this conventional system in that since the conventional system generally starts to cut off fuel supply during deceleration solely on the condition that the engine revolution speed is above a predetermined value, if the vehicular transmission should be in an excessively low gear at the moment of cut-off, the engine revolution speed will drop abruptly so that the total fuel savings will be insignificant while harmful exhaust components due to incomplete combustion may be emitted and passengers will still be subjected to an uncomfortable jolting sensation. These adverse effects are especially likely in cases where the vehicle has a power transmission, e.g., including a torque converter.
There is another problem in that since the conventional system resumes the currently cut-off fuel supply when the engine revolution speed rises above a predetermined limit, e.g. due to a long run of downhill or down-shifting of an automatic transmission to a lower gear position, and at the same time sets the fuel cut-off threshold speed higher than the engine revolution speed at which the fuel supply was first cut off, the total amount of fuel conserved may be less than is safely possible even though the fuel supply is cut off a second time.